This section is intended to introduce the reader to various aspects of art, which may be related to various aspects of the present invention that are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Radio-frequency identification (RFID) uses an object, an RFID tag (hereinafter “tag”), which interacts with transmitted radio waves, for example in systems for theft prevention, supply chain management or access to buildings. A typical tag comprises at least two parts: an antenna that receives and transmits a radio-frequency (RF) signal, and an integrated circuit that stores and processes information and processes the signal. Some tags, called “active”, comprise a battery and are thus autonomous, while “passive” tags have no battery and therefore have to rely on external power, often the received RF signal, in order to function properly.
It has been proposed, for example in WO 2006032613, to use tags on or in digital supports such as CDs and DVDs. This may for example be done in order to protect the content on the digital support (information necessary to access the content is comprised in the tag) or to store preferences regarding the playback of the content.
US 2008/0157974 A1 presents a solution in which a RFID tag may be disabled (and later re-enabled) based on time. The solution, which for example may be used at a video rental outlet, has an event, such as purchase of a DVD, activate a countdown timer. The RFID tag is then enabled until the countdown timer expires, after which the RFID tag is disabled. While this solution may achieve its goal, it is also somewhat limited as to the possibilities, as the countdown starts directly upon occurrence of the event and then inexorably counts down.
US 2006/250923 describes rotationally activated mechanisms to produce a modification to a data storage medium to render data thereon unreadable or inaccessible. These mechanisms, which include fluid-mediated mechanisms and mechanical switches, modify the medium physically, e.g. by altering the read surface of an optical medium, but they cannot be used to limit the time in any way as for instance US 2008/0157974 A1 can.
It can therefore be appreciated that there is a need for a solution that provides an alternative to the prior art. The present invention provides such a solution.